A stand-alone fusion cage is a fusion cage that has at least one angled hole in its anterior face for receiving a bone screw that passes through the cage an into an adjacent vertebral body. There are numerous conventional embodiments of these cages that capture the angled bone-engaging screw so as to ensure that the screw does not back out of the cage. Some of the known anti-backout mechanisms include: assembled rotating cover plates, cams, bushings, expanding screws, set screws and secondary cover plates that either snap onto the cage itself or are docked to the cage and secured to the cage faceplate using additional hardware such as a screw. These secondary cover plates can fully or partially cover the most proximal (anterior) portion of the screw head and would in theory prevent any screw backouts.
The following references are pertinent to the field of stand-alone cages: US 2008-0027550 (Link); US2010-0057206; U.S. Pat. No. 6,730,127; US2009-0088849; US2010-0145459; U.S. Pat. No. 7,662,182; U.S. Pat. No. 6,972,019; US2008-0249569; US2009-0105831; U.S. Pat. No. 7,306,605; U.S. Pat. No. 7,288,094; US2010-0312345; US2010-0286777; U.S. Pat. No. 6,945,973; US2010-0106249; U.S. Pat. No. 6,849,093; U.S. Pat. No. 6,984,234; US2009-0105830; US2009-0210062; U.S. Pat. No. 7,452,370; U.S. Pat. No. 6,558,423; U.S. Pat. No. 6,890,335; and U.S. Pat. No. 6,629,998.